Process for extracting pure nitrogen from air



R. M. HoRTvE-l E 2,314,827

March 23; 1943, PRoEss FOR EXTRACTING PURE NITROGEN FROM AIR 5 sheets-sheet 1 Origingl Filed Feb. 27, 1939 3 171:3 72 Inventor-z BB// March 23, 1943.` R. M. HoRTvE-T PROCESS FOR EXTRACTING PURE NITROGEN FROM AIR Original Filed Feb. 27, 1939 5 Sheets-Sheet 2 o .mu F

March 23, 1943- R. M. HoRTvE'r PROCESS FOR EXTRACTING PURE NITROGEN FROM AIR Original Filed Feb. 27, 1959 5 sheetsushet 3 ZIO Inventor-l:

YRich .B5

ard M.Hortvet Wj? tto rn g,

March 23, 1943.

R. M. HORTVET PROCESS FOR ExTRA'cTING PURE NITROGEN FROM AIR original Filed F'eb. 27. 1959 -shee'tssheet 4 Inv enter-z .ESX/24M R. M. HoR'rvE'r PROCESS FOR EXTRACTING PURE NITROGEN FROM AIR March 23, 1943.

s sheets-Sheet 5 Original Filed Feb. `27 ,.1959

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Inyzntor: crrd M. Hortvzet. Ba

Patented Mar. 23, 1943 Pnocnss Foa ExTaAc'riNG P Uan Nrrno- GEN FnoM Am Richard M.` Hortvet, Minneapolis, Minn., assignor to Diamond Iron Works, Incorporated, Minne,- y

apolis, Minn.

Original application February 27, 1939, Serial No. 258,658. Divided and this application February 5, 1940, Serial No. 317,312

( Cl. 2li-220) 2 Claims.

My invention relates to a process for extract# -ing pure nitrogen from air, and has for its object to take atmospheric air and pass it through a series of treatments whereby oxygen, carbon dioxide and water vapor will be removed and the residue of nitrogen will be obtained in a substantially pure condition.

Air, as is well known, is a mixture of gases, properly of the inert gas nitrogen and oxygen with small amounts of carbon dioxide and water vapor and practically negligible quantities of certain other gases. .Substantially pure nitrogen Vhas valuable uses in industrial technical procfrom the air substantially pure nitrogen at a cost low enough to make its use commercially prac-` tical in those industrial technical processes.

In carrying out this object in the practice of my process I subject a regulated current of air to a regulated current of fuel gas in combination with said air so as to obtain complete combustion of all oxygen and fuel thus brought together. The result of `this complete combustion will be a mixture of nitrogen, water. vapor and carbon dioxide, and I treat this gas mixture so as first to remove heat therefrom then to separate the carbon dioxide from the nitrogen and water vapor and nally to separate the water vapor from the nitrogen and recover the nitrogen in substantially pure form.

It is a further object of my invention in the practice of my process to subject the mixture of gases, nitrogen, carbon dioxide and water vapor, to regulated contact with a substance capable` of withdrawing the carbon dioxide from said mixture, and of carrying out this step of my process in such manner that all carbon dioxide wiu be withdrawn.

Itis a further object 'of my invention to employ a liquid agent such as monoethanolamine in a. properly concentrated solution and continuously to pass the gases of 'combustion under pressure through said solution in the form of vast numbers of very minute bubbles, and of circulating the solution continuously and removing the carbon dioxide content thereof as the liquid is circulated'.

It is a further object of my invention to pass the mixture of gases, after the carbon dioxide has been removed, in intimate contact with substances such as silica gel or alumina by which water vapor will be removed therefrom and thereafter to recover and store for use, resulting sub'- stantialiy pure nitrogen.

Itis a further object of my invention to maintain the processes continuously by reactivating part of the dehydrating material at the same time that another part is employed in dehydrating and by shifting the now of gases from one body of dehydrating material'to the other so that the process may be carried on continuously. I

It is a further object of my invention to emploir the heat withdrawn from the hot furnace gases for aiding in heating the'liquid carbon dioxide adsorber to drive off carbon dioxide. The

essential purpose of my process is to operate upon air so as to reduce all oxygen in the air to carbon dioxide to separate from the resulting mixture of nitrogen, carbon dioxide and water vapor, all of the carbon dioxide and water vapor in said mixture and to carry on vthe steps of the process continuously whereby air treated at the beginning will be reduced to pure nitrogen discharged at the end of the'process-of its operations.

Thefull objects and advantages ofmy invention appear in connectionwith the detailed-description thereof and its novel features by which the advantageous results of myv process are obtained will be particularly pointedr out in the claims.

A form of apparatus for carrying out the various steps of my process is illustrated in the drawings, and is claimed in my application Serial Number 258,658, illed February 27, 1939, of which this is a division, but it is not to beunderstood that the practice of the process is limited to the form of the invention disclosed in the accompanying drawings. In these 'drawings- Fig. 1 is aside elevation view of the entire Fig. 7 is an end .elevation view of the 'entire I apparatus viewed from the nitrogen removing end of the same with the condenser for carbon l dioxide absorber shown in section. Fig. 8 is a sectional view takenon line l-I of Fig. '1. y

Fig. 9 is a sectional elevation view of a part of one of the dehydrators.

Fig. 10 is .a sectional view taken on line III-4N of Fig. 9.

Fig. 1l is a sectional view ofthe cooler for cooling the gases of combustion. y

Fig. 12 is a sectional fview taken on lineV |2-l2 of Fig. 1l.

Fig. 13 is a sectional elevation view of a heat exchanger used as an aid in both heating and cooling the absorber liquid in the process of reactivating it.

Fig. 14 is an end elevation view of the apparatus taken from the opposite end of the view shown in Fig. 7.

Fig. 15 is an enlarged sectional view of valve mechanism for controlling ow of fuel gas and of air. i

Fig. 16 is an enlarged detail view of the valve member taken substantially along line Iii-I6 of Fig. 15 but shown in perspective.

Fig. 17 is a sectional elevation view taken through the body of the carbon dioxide removing or scrubber tank.

Fig. 18 isa sectional elevation view taken through the main body of the burner and combustion chamber including the cooling and airheating means.

Fig. 19 is a sectional view taken on line I9-I9 of Fig. 18.

In the practice of my process it will be apparent that the first step must consist in complete reduction of oxygen in the air. But this step must be carried out without contaminating the resulting mixture with fuel gas. The fuel will be preferably in the form of gas, arid the mixture of this gas with the incoming air must be so proportionate in relation to the form` of combustion that complete chemical union takes place between all of the-fuel supplied and al1 of the oxygen in the gas. The resulting gas mixture, which is terrically hot, has to be cooled after which the cooled gas is passed through or about some substance to remove the carbon dioxide from the gas. I have found the liquid known as monoethanolamine to be highly satisfactory for the purpose, A third step in the treatment of the gas consists in taking it from the scrubber where it has been subjected to the carbon dioxide removing chemical, into intimate contact with some water adsorbing substance such as silica gel or alumina, of which I have found alumina to be very satisfactory, and which will remove the water from the gas mixture leaving substantially pure nitrogen which may be passed to any desired means of storing it or compressing it in tanks for future use.

The monoethanolamine or other substance used for removing carbon dioxide to make the process effective and economical must be continually reactivated. That is, the carbon dioxide taken up therein must be driven off. This is effected by passing the monoethanolamine through instrumentalities which include a boiler, since boiling the liquid will drive off the carbon dioxide and the liquid monoethanolamine must afterwards be cooled before being returned to the scrubber. A second supplemental feature of the process requires that a continuously-operative dehydrating tower be available at all times, which necessitates reactivating the dehydrating material, whether it be alumina, silica gel or the like, and means has been provided for having two towers, in one of which the dehydrating material is being reactivated while the other is being used as a dehydrator, together with means for delivering hot air to the tower wherereactivation is taking place and delivering cooled air, to take away the heat releasedl in dehydration, to the dehydrating tower used to take the water vapor from the nitrogen gas.

These several sets of instrumentalities emtaken up in order.

. bodying the several steps of my process will be Generating the combustion gas mixture A cylinder I0 stands vertically and as shown in Fig.` 18 is provided with inner and outer shells II and I2 with heavy insulation I3 between these Walls. At the bottom of this cylinder is a combustion block I4, shown in detail in Fig. 18, which comprises an outer metallic shell I5, refractory insulation I6 and a refractory combustion block I1 having therein a vertical passage I8 which communicates through an expanding passage I9 with the burner throat 20. It will be understood that when the gas is being burned the block I1 becomes exceedingly hot, so that the mixture of gas and air is burned in a passageway I9, I8, the walls of which are heated to a very high temperature, and this is essential to secure the one hundred per cent union of oxygen and gas fuel to produce, with the nitrogen of the air and any water vapor carried by the air or generated in the combustion, a hot gas mixture which'contains in addition to nitrogen and water vapor only carbon dioxide. A chamber 2I above the burner block I1 receives the hot gases from the mouth 22 of the burner passageway I8, where the hot gases expand under further great heat and nal union of oxygen with the carbon of the fuel completes the reduction of fuel and oxygen of the air so as to combine all of the oxygen of the air with all of the fuel.

The burner head 23 is indicated generally in Fig. 14 and in a larger outline in Fig. 18, while its details are shown in enlarged section in Figs. 2, 3 and 4. Gas from any source of supply is delivered through pipe 24 which passes through a flow meter 25 of usual construction. Customarily gas from city mains will be employed and ordinarily during any working period the B. t. u. content of the gas will remain substantially constant. If however, conditions of variation of B. t. u. content are met with, it may be desirable to employ well known controls, not shown, for insuring a constant B. t. u. content of the fuel gas, and this I contemplate doing.

'Ihe gas employed for combustion before reaching the burner 23 passes through a valve structure 26, shown in enlarged detail in Figs. 15 and 16, by which the flow of gas to the burner may be very exactly adjusted. This valve comprises a body 21 having formed thereinl a chamber 28 which is separated from a second chamber 29 in the valve body by meansof an apertured diaphragm 30. A valve seat 3I-is formed about said aperture and is engaged by the valve face 32 on a valvemember 33 controlled by a hand wheel 34, as clearly shown in Fig. 14. Upon the valve member 33 are integrally secured a series of wings 35, shown somewhat in detail in Fig. 16. wings have their outer surfaces lying in the surface of a cylindrical plane and diverge along their edges from each other as indicated at 38. The result is .that as the valve is lifted only small port openings at the top or point of joinder of the wings 35 will be formed, and through these openings the gas from pipe 24 and chamber 28 i These to casting 38 by means of a setbolt 45. The castlng 43 is formed with a chamber 46 which entirely surrounds a cylindrical extension 41. of cast ing 38 and tube 4|, as clearly indicated at 48 in Fig. 2. Air under pressure from a source later to be described passes through a tube 49, ow valve 50, control valve and pipe 52 into the chamber 46, 48. It is to be noted that the valve 5| is in all respects identical with the valve 26 heretofore described and operates to control the dow of air under pressure in the same manner as valve 26 controls the flow of fuel gas. Hence the air under pressure entirely surrounds extension 41 and tube 4| within chamber 46, 48. The extension 46 isl provided with a series of holes 53, all centering in a circumference of extension 41, and. tube 4I has holes 54 similarly disposed circumferentially so that each hole 54 is adapted to register more or less with a hole 53, as clearly shown in Fig. 3. The tube 4| is held positioned ln casting 38, as shown in Figs. 2 and 4. A thumbscrew 55 is threaded into the casting 38 as indicated at 56 and carries a stem 51 having thereon a disc 58 which takes into a. slot 59, best shown in Fig. 2. And a set screw 60 has a pin-like extension 6| which takes in a circumferential slot l2 in tube 4| to hold .it-free for rotary movement but restrained against longitudinal movements. It follows that when the thumbscrew 55 is turned lt will move the disc 58 in or out, owing to the threading at 56, and this willoperate to turn the tube 4| more or less, causing the holes 54 therein to register more or less with the holes 53 in extension 41, thus effecting delivery of more or less air to the annular passageway about tube 39.

It will be observed that the air is thus delivered in a cylindrical sheet about the delivery of gas from tube 39 at its outlet 40 andthe gas will thus .travel to the burner mixed with the air but with a greater proportion of air at the outside of the stream of combined gases. This efhot gases going through pipe 63, is carried through` pipes 15and 16 to a distributing chamber 11 for a use which will later be described and cold air from distributing chamber 12 goes through pipes 18 and 19 to a distributing chamber 80 for a. usewhich will later be described.

By. the time the gas mixture reaches chamber 64 it will have given up a large part of its heat to the air leaving the chamber 64 through pipe 15. 'I'his partially cooled gas is carried through pipe 8| to a cooler 82, Figs. 5 and 14, which is shown in detail in Figs. l1 and 12. 'I'he cooler is supplied with-water from any system through pipe 83 which leaves through pipe 84 and goes to waste. l

The gas mixture will leave the cooler 82 at 85, Figs. 11 and 14, from which it goes through pipe 86 to a pump 81 operated by a motor 88 connected to pump 81 by belt-and-pulleyconnection 89, Fig. 5. From pump 81 the gas is delivered under pressure. through pipe 90 to a pipe 9|, Fig, 1, which puts the gas into the bottom of an absorber cylinder 92.

The cooler 82 comprises a chamber 93 formed with heads 94 and 95 in which is seated a multiplicity of tubes 96, as clearly shown in Fig. 12. A space 91 under partition 94 receives the water from pipe 83 and distributes it through the various tubes 96 to be delivered into a space 98 above partition 95, from whence it goes through pipe 84 to waste. The gas from pipe 8| is caused to flow in chamber 93 about the tubes 96, made cold by the water flowing through them, which fect's more intimate contact of all of the mole- Cooling the hot gases of combustion From expansion fire chamber 2| above surface I8 of burner block I1 the combustion gases comprising nitrogen, carbon dioxide and water vaporwill pass through a series of passageways 63 formed in a chamber 64 in the upper part of the cylinder to adelivery chamber 64' at the top. A sealing lid 65 opens through a sight hole or handhole 66 into chamber 2|, and a sealing lid 61 similarly Opens through a sight hole or handhole 68 into chamber 64.` The tubes 63 are surrounded with air which enters chamber 64 as cold air at the top of cylinder at the point 69 and which leaves as hot air toward the bottom of said chamber at 10 as very hot air. The air comes from any suitable source of supply of compressed air, not shown, through a tube 1|,

results in removing the additional heat from the gas so that it leaves pipe 85 at near room temperature. Since the cooling of the gas greatly diminishes its bulk, best results have been obtained by making the entrance pipe 8| considerably larger than the exhaust pipe 85.

Removing carbon dioxide from the gas As above stated, the cooled mixture of gases pumped from the cooler 82 goes through pipe 9| under pressure, Fig. 1, into a feed tube 99,`

Fig. 17, which delivers into a cylindrical chamber |00. The chamber |00 -is surrounded by a drum |0|, the cylindrical Walls |02 of which are spaced annularly from the cylindrical walls |03 bearing at ||0 in a socket member secured Fig. 14, from which it goes to a distributing cham- I :emperature by heat exchange with the intensely in an extension ||2 on a bottom closure ||3 which is fastened by means of bolts ||4 to the bottom of the scrubber cylinder 92. The cylinder 92 is closed at the top by a cap ||5 secured by bolts 6 to an annular flange ||1 about the upper end of cylinder 92. The shaft |09 goes .through a stuiling box ||8 on cap ||5 and is `Within the cylinder 92 is a liquid absorber of carbon dioxide, and for the purposes intended I have found the liquid compound known as monoethanolamine in a thirty per cent solution to' be highly effective and satisfactory. The

upper level of this liquid will be maintained atl a point indicated by dotted line at |24. Below this point there is a passageway |25 in tank- 92 which is extended into a small tank |26 at one side of cylinder 92 in `which the liquid reaches the level indicated at |21, which is substantially the same as the level |24 in cylinder` 92. Apipe |28 is'adapted to withdraw the liquid from small tank |26 for reactivation thereof, as hereinafter described. A connection |29 leaves the top of small tank |26 at the point |30 and communicates with chamber in cylinder 92 through opening |3|.

The above instrumentalities for freeing the furnace gases of carbon dioxide function in the following manner:

The mixture of gases from the cooler is forced under pressure of pump 81 through connecting pipe 9|' and delivery tube .99 into distributor chamber |00, going from there through aper tures into annular passages |01 above and below and between the separator blades or discs |04, and within cylinder |02. From these spaces the gas is--driven through small apertures |22, and because of 'the comparatively rapid rotation of the walls of drum |0l| and of these apertures with it the gas moving through them is broken into an enormous number of minute bubbles. At the same time these bubbles are given a rotating movement in the whole mass of liquid within .the cylinder 92, whereby their path of travel from the point where formed to their discharge at surface |24 will be a very long helix. Because of their small size and consequent relatively large surface resistance these bubbles move upwardly through the body of liquid to discharge from its surface |24 over this long helical path in a manner greatly to retard their movement through the liquid so as to hold them in the liquid a relatively long time. Further, because of the minute size of the individual bubbles of gas, such complete and long contact of all the gas comprised in the individual bubbles is effected that complete absorption of theA carbon dioxide therein` by the absorber liquid takes place. And this is done in an absorber tower of very moderate height.

The tiny bubbles of gas break through the surface |24 and pass through apertures |23 in rotating disc 2| and about the edges of said disc whereby any entrained liquid will be precipitated and thrown to the walls of the cylinder 92 from which the liquid will gravitate back into the main mass at |24. The gas, freed from all carbon dioxide, then goes to the space |32 at the -top of tank 92, from which, still under pressure from pump 81, it is caused to pass through pipe |33 to the dehydrators later to be described.

The `absorber liquid, such as monoethanolamine,

goes through passageway |25 into tank |26 where it is freed of its contained bubbles of gas at the surface |21 of the liquid within small tank |26, and moves from there through pipe |29 Removing water 'vapor from nitrogen gas The gases freed from carbon dioxide go through pipe |33, Figs. 1 and 5, to a distributor chamber |34. As clearly shown in Fig. 5, the distributor chamber |34 has branches |35 and |36 which lead past valves |31 and |38 through short pipes |39 and |40 to one or the other of the tops of dehydrator towers |4| and |42, one of which is shown in detail in Figs. 9 and 10. By manipulating the valves |31 and |38 gas can be made to go through either of the dehydrating towers |4| or |42 as desired, and according to which of these has been reactivated for its de' hydrating function.

As shown in Figs. 9 and 10, dehydrating tower |4| (and |42) comprises an outer shell |43, an insulating lining |44 and an inner drum |45. As clearlyshown in Figs. 9 and 10, the drum |45 lis spaced at |46 from the inner walls of the insulating material |45 and is providedwith a, multiplicity of passages |41 extending longitudinally through the drum. The drumI except for the vertical passages |41, is entirely lled with some dehydrating material |48 such as silica gel or activated alumina. I have found that activated alumina, on account of its comparatively large granular size, is an effective and desirable material for dehydrating the gas mixture.

The pipe |39 leads directly into the top of drum |45, as shown in Fig. 9, and an outlet pipe |49 leads from the bottom of drum |45.

The functioning of the above instrumentalities is that the mixture of nitrogen and water vapor leaving the absorber tank 92 through pipe |33 in passing through the dehydrator drum |45 flows slowly around and through vthe passages between the mass of dehydrating material |48 in said drum, and during such passage has removed therefrom substantially all water vapor carried by the gas mixture. The gas that leaves the dehydrating tower through pipe |49, is therefore, substantially pure nitrogen. -It isto be noted that a similar pipe |50 extends from dehydratoz tower |42, Fig. 7, and the gases go from tower |4| through pipe |49 and past valve |5| to a distributor chamber |52, while the gases go from tower |42 past valve |53 to the distributor chamber |52. From the distributor chamber |52 a pipe |54 conducts the pure nitrogen gas to any suitable means for compressing and storing the same.

Reactzinltiny thedehydrating material Since to obtain the nitrogen at a low cost it is ,essential that the above process' work continuously, there must be a plurality of dehydrating towers with means for reactivating the dehydrating material in-one while the other is in use for dehydrating the gas. The two towers |4I, |42 have already been generally described and the means of shifting from one tower to the other through valves |41,`|38 and valves |5|, |53 has been described, it being understood that valves |5| and |53 are operated in the same way as valves |31 and |38. In order to reactivate the alumina |48 or other dehydrating material it is necessary to heat it to a fairly high temperaturesay around 300 Fahrenheit. I effect this heating economically by takingthe heated air from the combustion tower.|0. at the distributor chamber 11, past one or the other of valves |55 or |56, Fig. 5, Vthrough branch pipes |51 or |58 to the bottom of dehydrating tower I4] or |42 and to a manifold- |59 therein, Fig. 9. This manifold, as shown in Figs. 9 and 10, is provided with aseries of nipples |60 each positioned below themouth of one of the pipes |41, whereby heated air is driven through the passageways and also around the drum |45, this heated air discharging to atmosphere through the opening |6| in the top of the dehydrating tower.y Under some conditions the air heated by heat exchange with the furnace gases in the upper part of combustion tower may not be suiiiciently heated to eiectively reactivate the alumina |48 or other dehydrating material, and to remedy. this deficiency, where it exists, I provide a gas burner |62, Fig. 9, in the lowerpart of each of dehydrating towers |'4| and |42 supplied by gas from any suitable Source, not shown, through pipe |63. The gases of combustion from this burner will further heat the air delivered from the nipples |60 by heating manifold |59 and will deliver a cylindrical sheet of heated gas aboutI the outside. of the drum |45, whereby all of `the material |48 within the drum'wwill be heated to the desired temperature and the reactivation of the material by removal of absorbed'water therefrom will be effected.

When the water vapor leaves through either pipe |39 or pipe |40 it will condense in said pipes. Since`these pipes will be blocked by valve |31 or |38 the water vaporwill go out of the opening controlled by. pet cock |64 provided in pipes |39 and |40. To aid in the removal of the generated steam or water vapor resulting from heating and consequently reactivating .the dehydrating material, I provide a pipe |65, Fig. 1, having therein the valve |66 by means of which nitrogen may be forced into the bottom of the dehydrating drum |45 of either tower |4| or |42 through either vpipe |49 or pipe |50, and owing through the dehydrating material |48 will purge out the last of the entrapped steam in said material.

After the dehydrating material has been properly reactivated, and before it can be used for absorbing moisture from the nitrogen gas, it is necessary to cool the same. Further, the heat as tetramine and monoethanolamine. Tetramine has greater capacity for absorption than monoethanolamine,but has corrosive characteristics which I have found make monoethanolamine a more satisfactory liquid for the purpose.

'I'he manner of using the monoethanolamine to take the carbon dioxide out of the mixed gases has been heretofore described. It is obvious, however, that in order to keep the process operating continuously it isnecessary continuously to reactivate the monoethanolamine by removing therefrom the absorbed carbon dioxide, and the means for doing this will now be described:

Referring to Figs. 1 and 5, the liquid absorberl material is drawn through pipe |28 and small. tank |26 by means of a pump |13 operated by a motor |14 through belt-and-pulley connection |15. The pump |13 drives the liquid through a pipe |16 to the top of a heat exchanger |11, as clearly shown in Fig. l. The details of this heat exchanger are shown in Fig. 13. The heat exchanger |11 as there shown comprises a lower chamber |18 and two upper chambers |19 and |80. The monoethanolamine enters chamber |19 from pipe |16 and passes through a multiplicity of tubes |8l, all of which open into chamber |18 and half of which open into each of chambers |19 and.|80. The monoethanolamine enters chamber |19 from the pipe |16, passes through part of the pipes |8| to chamber |18 and from chamber |18 through the rest of the pipesto chamber |80, from which'it passes through pipe |82, Fig. 5, to a boiler |83, which is shown in detail in Fig. 6. This boiler comprises an outer insulated shell |84 with a bottom burner chamber |85 in which is a gas burner |86 supplied with gas through pipe |81 from a source of gas supply not shown. The burner chamber is supplied with air through openings |88 and the of dehydration released by the action of the |51, |58, as shown in Fig. 5 and indicated in dotted lines in Fig. 14 at |1| |12. VIt follows that by manipulating the valves and |56 for the hot air. Fig. 5. and the valves |61and |68 for the cold air, Fig. 14. the hot air may be delivered to one of the towers. as towery HH.` and at the same time cold air be delivered to `the other.-

of the towers, as tower |42. and thus the vreactivation of the dehydrating material in one tower and the cooling of said material in' thefother tower may be carried on simultaneously.

Reactivatng the carbon dioxide vabsorberv Y material f There are a number of chemical liquicl'sl which gases of combustion pass around a boiler chamber |89 within the insulated shell |84 and through numerous tubular passages |90 extending through the boiler member |89 and from the top thereof into a conical member |9| which discharges to atmosphere at |92. monoethanolamine, preheated in the heat exchanger `|11, passes from pipe |82 into boiler chamber |89,y where'it reaches a normal level, indicated by the dotted line |93 which extends across the bottom of an annular steaming chamber |94 in the top of the'boiler chamber and into a small expansion tank |95 communieating with the boiler by means of a passageway |96, all as shown in Fig. 6.

The waterI level line |93 is at atmospheric pressure and the released carbon dioxide gas with some monoethanolamine vapor passes directly from the top of small tank |95 to pipe |91. Likewise,' the carbon dioxide and vapor released in the top of the chamber |94 passes through' pipe |98 to pipe |91.

The liquid monoethanolamine moves into .l small tank |95 through passageway |96 and discharges from thebottom of tank |95 through a :ff pipe |99. clearly indicated in Fig. 5 and indicated in dotted lines in Fig. 7.

y The pipe |99, as shown in Figs. 5 and 13, enters the heat'exchanger chamber-200 at a point near its bottom,

"as indicated at 20|. :boiler lls the chamber 200 to a point 202 near the top thereof. Fig. d13, from which'it flows by have the property of absorbing carbon dioxide from a gas mixture, and which when subjected to heat will upon boiling dischargethecarbon dioxide. Among these liquids arev such substances n' The hot liquid from the gravity through pipe 203 to a second pump 204,

Fig.. 5, which is 'operated by the second belt-andv -pulleydrive 205 from motor |14.' The very hot wliqud loses. a considerable part of its heat in The liquid heat exchanger |11 and is passed from pump 204 through piping 206 to a cooler 201, which is similar in its internal construction to heat exchanger |11 heretofore described, and shown in detail in Fig. 13. From the cooler 201, as clearly shown in Fig. 5, the cool ronoethanolamine goes through piping 208 to a point 209 at the side and near the bottom of the scrubber or absorber tank 92 and into it at that point.

Since there will be a considerable amount of vapor of monoethanolamine driven off at surface |93 in the boiler and supplemental tank |95, it is necessary to employ a condenser to recover such monoethanolamine vapor. This condenser is shown in Figs. 1, '7 and 8, and comprises a cylinder 2|0, which is perfectly mounted at an angle, as shown. This cylinder comprises a multiplicity of tubes 2| I, all of which open into a chamber 2|2 at the lower end of cylinder 2|0 and part of which open into a chamber 2|3 and part in a chamber 2 I4 at the top of cylinder 2|0. The pipe |91 carrying the CO2 and vapor from the boilerl |9| discharges these gases into chamber 2|3, from which they pass through a portion of pipes 2|| into chamber 2|2 and back through the remainder of pipes 2|| into chamber 2|4. From chamber 2M the carbon dioxide gas exhausts to atmosphere through port 2| 5. monoethanolamine condensed in the passageways 2|| gravitates through pipe 2|6 and joins' with pipe |99 through which it moves with the rest of the monoethanolamine to the lower prtion of heat exchanger |11.

' The water circulation Which has heretofore been described as going through the cooler 82 also goes through cooler 201 and condenser |95. Water pipe 83 leads into cooler 201, as indicated at 2|1, Figs. 5 and 7. From cooler 201 pipe 2|8 leads to the point 2|9 where it enters'condenser 2|0, Fig. 7. From condenser 2|0 pipe 220 leads to the water system from which water is supplied under pressure.

From the above it will be seen that the water flows rst through condenser 2|0, then through cooler 201 and finally through cooler 82, from which it discharges to the sewer through pipe 84.

The advantages of my `invention will be apparent from the foregoing description. The primary and highly important utility is the recovery of nitrogen of a high degree of purity in large quantities and at very small expense. The

quantity of nitrogen recovered from any plant embodying the steps of my process and apparatus' for carrying it ou.. can be determined by the size of the plant. I havefound, however, that it is practical to provide different sizes of plants practical and effective in operation for the production of nitrogen at rates from 100 cu. ft. per hour to 3,000 cu. ft. per hour.

It will be apparent that in order to accomplish these results and obtain the economies desired, and which are essential for the production of nitrogen for the more general commercial uses, the continuous uninterrupted operation of the plant and all of its component parts is required. This continuous operation can only take place when there is continuous reactivation of the carbon dioxide absorber liquid and of the dehydrating material. It is a feature of great advantage in my process that the reactivation of these materials is effected largely by heat saved through heat exchange with both the burning of gas and air to obtain the oxygen-free mixture of gases. and with the heated absorber The vand operates to produce large volumes of substantially pure nitrogen from the al1` at not only.

a relatively low cost of production but also at a relatively low cost of the apparatus making up the plant.

I claim: A

1. A process of obtaining nitrogen from air which consists in causing a stream of fuel gas and a surrounding stream of air to unite at an ignition point, effecting ignition of the gas within the surrounding Aenvelope of air at that point, thereafter lcontrolling expansion and forward movement of the gases of combustion by means of walls of a refractory block so the same will continually expand diametrically for a predetermined distance through said block, at the end of said distance causing the direction of movement of the ignited gas to be changed sharply by impingement against walls of said refractory block, whereby the Whole body of said refractory block and particularly the said constraining walls thereof become heated to a very high temperature to cause complete union of all the molecules of the fuel gas'and of the oxygen of `the air introduced at said ignition point, the combustion gas mixture and the nitrogen therein being maintained in continuous motion from the point of burning to the place where the finally separated nitrogen is accumulated, cooling the resulting gas mixture, thereafter causing the cooled gas mixture to move in an elongated helical path in fine bubbles in a solution for absorbing carbon dioxide to remove the carbon-dioxide therefrom, then removingwater vapor therefrom, leaving substantially pure nitrogen, and accumulating said nitrogen for use.

2. A process `of obtaining nitrogen from air which consists in causing a stream of fuel gas and a surrounding stream of air to unite at an ignition point, regulating the relative volumes and delivery rates of the fuel gas and air so that the number of molecules of oxygen in the air relative to the number of molecules` of the fuel gas will permit complete union thereof without residuum of either upon combustion, effecting ignition of the gas within the surrounding envelope of air at that point, thereafter controlling expansion and forward movement of the .gases of combustion by means of walls of a refractory block so the same will continually expand vdiametricallyfor a predetermined distance through said block, at the end of said distance causing the direction of movement of the ignited gas to be changed sharply by-impingement against walls of said refractory block. whereby the whole body of said refractory block and particularly the said constraining walls thereof become heatedto a Very high tempera.- ture to cause complete union of all the molecules of the fuel gas and of the Oxygen of the air introduced at said ignition point, thereafter removing carbon dioxide from the resulting gas mixture and then removing water vapor therefrom, leaving substantially pure nitrogen, and accumulating said pure nitrogen for use, the combustion gas mixture and the nitrogen' therein being maintained in continuous motion from the point of burning to the place where the finally separated nitrogen is accumulated.

RICHARD M. HORTVET. 

